The following description relates generally to a method for testing impact resistance of a glove, and an apparatus for performing such a test.
A human hand includes a number of bones, major nerves, arteries, veins, muscles, tendons, ligaments, joint cartilage, skin and fingernails. Worksite injuries to hands sometimes include injuries to one or more of the hand parts listed above. Such injuries may require medical attention which may result in worker and/or worksite downtime as well as large healthcare and/or insurance costs.
Impact-resistant gloves have been developed in an effort to reduce hand injuries. Impact-resistant gloves typically include high density thermoplastic rubber pads or overlays positioned along a top or back side of the glove, corresponding to a back of a wearer's hand, and along fingers to protect from impacts. Some impact-resistant gloves may also include padded palms, molded knuckle areas and extra grip patches.
Standard testing protocols have been developed by organizations, such as the American Society for Testing and Materials (“ASTM”), for testing impact resistance of various products. Following such standardized procedures, impact resistance may be compared across different products. One such testing standard is ASTM 1446-12. Under ASTM 1446-12, performance characteristics of a protective headgear may be evaluated. ASTM 1446-12 requires a mass, approximately 3 to 6 kg to be dropped and impact attenuation is measured. An impactor is secured with the protective material or head gear.
Another standard, ASTM F1937-04, provides a standard specification for body protectors used in horse sports and for horseback riders. In ASTM F1937-04, a 0.5 meter drop of a mass creates an impact velocity of 10.33 feet per second (ft/s). The peak acceleration (impact attenuation) of any impact shall not exceed 300 g. The inbound velocity, gmax (maximum acceleration) and deformation depth are recorded for each impact.
Still another standard, ASTM F2412-11, relates to standard test methods for foot protection. In ASTM F2412-11, a 22.7 kg mass is dropped onto a wax form to create an impact of 75 ft-lb. A distance from a lowest point in an impression made in the wax form is measured.
Another standard, EN (European Standard) 13594, relates to protective gloves for motorcyclists. Under EN 13594, in order to pass the test, a transmitted impact force through a test glove cannot exceed 4 kN (900 lbs) after being impacted by 5 J (3.7 ft-lb) of energy.
Another test for determining impact protection is described in the EN 1621-1 standard. The EN 1621-1 standard relates to a test for determining impact resistance of protective motorcycle armor. In EN 1621-1, a piece of motorcycle armor is disposed on a 50 mm radius hemispherical dome or anvil mounted on a load cell. A 5 kg mass with an 80 mm×40 mm flat striking face is dropped from a height sufficient to create an impact energy of 50 J onto the armor. The force transmitted through the armor is measured by the load cell. A mean maximum transmitted force is not to exceed 35 kN in order to pass the test, and no single value should exceed 50 kN.
Another test is commonly referred to as the “wood block test.” In the wood block test, a test object is placed on one or more wood blocks. The test object may be an intact glove or a back of the glove split from the palm. The wood blocks are supported at their ends and extend across a gap. A mass is dropped onto the sample, imparting a force that is transferred to the wood blocks. If a sufficiently large force is transferred to the wood blocks, the blocks will fail. This may occur in situations where the sample does not have adequate impact protection. When the sample includes adequate protection, the wood blocks may remain intact after application of the impact force.
However, neither ASTM nor the European standards provide a test for measuring a reduction in hand impact force. In addition, none of the standard test protocols described above, or other similar test protocols, use a weight suitable for testing impact resistance or protection on a back of a glove, as the weights or masses involved in the tests above exceed weights or masses that could cause hand injuries if applied to a glove in a work environment scenario. That is, in the tests described above, the energy imparted on the glove or other test object (e.g., motorcycle armor or head gear) is higher than that which typically causes hand injuries. As such, these tests do not test gloves at a practical level of force where hand injuries may be avoided or mitigated.
Further, in the above tests, the striking face of the mass or impactor is unsuitably large for simulating impacts that are imparted on work gloves during use in work environments. That is, in the tests above, a striking face may be so large that the impact is distributed across a large surface of glove. As such, impact resistance of smaller, particular sections of the glove, for example, those sections corresponding to joints of the hand or knuckles, cannot be accurately determined. Other tests, such as the wood block test, are not scientific and may not be reliably repeated to obtain consistent quantitative data or accurate comparisons between test objects.
Some glove manufacturers have developed other tests, or use portions of standard tests, in an effort to determine or measure impact resistance. For example, in one test, carrots are inserted into a glove as a substitute for fingers. A 3.5 lb pipe is dropped onto the glove from approximately 16 inches. However, this test is suitable for demonstration purposes only, and lacks scientific value. For example, such a test cannot be reliably repeated and results cannot be reliably reproduced. In addition, carrots are poor models for human fingers. This test may also refer to ASTM D2632, which is a vertical rebound test that is not directly applicable to impact protection. That is, ASTM D2632 is not scientific for testing resistance to impact. Rather, ASTM D2632 compares the viscoelastic or bounce-back properties of materials.
Another test is a combination of the wood block test described above and the EN 1621-1 test. In such a test, a glove is placed either intact or split back from the palm on a load cell. A mass is dropped on the glove and the load is measured at the load cell via a computer interface, under EN 1621-1. However, as discussed above, the wood block test is not scientific and results are difficult to reproduce.
In still another test, a glove is mounted on a mandrel and a mass is released onto the glove and mandrel with a toggle. The test may use a twin rail design for movement of the mass and results may appear on a dial, also supported by the twin rail. However, in such a test, use of the mandrel does not allow for a wide range of testing at different locations on the back of the glove. In addition, the dial readout may be inaccurate.
In still another test, a glove is placed intact, or possibly filled with a ballistics gel, on a support surface. A weight block with a mandrel is released from a specified height and the impact force is measured by a load cell. However, in this test, measuring the load of an intact glove measures the impact resistance of both the back of the glove and the palm of the glove, and in some cases, the ballistics gel. Thus, the load cell measurement is not a measurement of impact resistance at the back of the glove alone.
Other impact tests, as well as those above, do not take into consideration or measure a precise impact resistance of the glove at specific points of impact.
Accordingly, it is desirable to provide an impact resistance testing method suitable for measuring a transmitted impact force (i.e., impact resistance) through a glove at at least one location, and preferably, at each of a plurality of locations. It is also an object to provide an apparatus for performing such a test.